1. Field of the Invention
The present invention relates to a pneumatic vehicle tire having a radial carcass and a belt-like reinforcing member of at least two cord plies, at least one of which comprises steel cords. The cords of adjacent plies cross one another, and at least one of the cord plies has a width corresponding approximately to the width of the tire tread. Cap ply means are disposed radially outwardly of the belt member and are comprised of rubberized, non-metallic heat-shrinking reinforcing elements that extend parallel to one another in the circumferential direction of the tire, and extend more than completely around the belt member, at least in the edge regions of the latter, to securely hold these edge regions in place.
2. Description of the Prior Art
Pneumatic tires of this type are reinforced by multi-layer belt members disposed in the region between the carcass and the tread. Depending upon the type and size of the tire, the reinforcing belt member comprises at least one steel ply and one fabric ply, or two or more steel plies.
To protect against separation of the edges of the belt, and to keep moisture from the belt member to the greatest extent possible, additional cap ply means are provided. Such cap plies comprise heat shrinking textile filaments or cords that are oriented in the circumferential direction of the tire. These cap plies extend around the belt member, and in addition impart advantageous properties to the tire. For example, a more favorable rolling resistance and a greater riding comfort are provided. In addition, such cap plies, which are known as safety belts, are very suitable for high speeds, and have a safety reserve.
Pneumatic tires of this general type are known, for example, from U.S. Pat. No. 4,284,117 Poque et al dated Aug. 18, 1981, the text of which is incorporated herein by virtue of this reference thereto. The reinforcing elements of this heretofore known cap ply comprise multifilament individual threads having twists of approximately 100 to 400 per meter.
These cap plies to a large extent protect against the effect of moisture. However, they do not adequately reduce the creepage of moisture over time.
An object of the present invention is to eliminate movement of moisture particles due to the more or less large creepage movement caused by the movement of air within the cord elements of the cap ply, and hence to also eliminate the adverse effect upon the belt plies held in place by the cap ply, or at least to keep such effects to a minimum and within permissible limits over a longer period of time. In this way, the steel cord elements of the belt plies are protected against reduction of the adhesion of rubber to steel, and the steel wires are protected against corrosion.
A further object of the present invention is to construct the additional cap plies of heat shrinking commercial filaments in such a way that the construction of the cords or the yarns themselves is airtight, and thus impermeable to moisture.